The present invention is related to fittings or inserts that are used to pass pipes, cables, wires, etc. through a shell or wall that forms a pressure boundary, e.g. the bulkhead or shell of a vessel. In certain prior art fittings, called stuffing tubes, a single tube is provided for each wire or cable that is to be passed through the bulkhead.
To prevent the structural integrity of the bulkhead from being compromised, the stuffing tubes must be sufficiently spaced. This limits the number of tubes that may be installed in a given bulkhead or area of a bulkhead. In existing vessels, especially submarines, the area available for the installation of stuffing tubes is limited and fully occupied with existing stuffing tubes. Adding new circuits with wires or cables that must pass through these areas is difficult, if not impossible.
A solution proposed in the prior art is a single penetration fitting that allows a relatively large number of pipes or cables to be brought across a relatively small area. This solution is disclosed in U.S. Pat. No. 4,819,971, issued to the inventor of the present application and assigned to the same assignee as the present application. In the U.S. Pat. No. '971 fitting, a number of straight channels are drilled through a single penetrator, each channel permitting passage of a pipe or cable. In one embodiment, transverse channels are drilled into the ends of the penetrator and meet the straight channels at a right angle. This, in effect, increases the end surface area over which pipes can be fitted onto the penetrator.
The straight channels of the U.S. Pat. No. '971 fitting, while suitable for many applications, present certain disadvantages when the U.S. Pat. No. '971 fitting (or the prior art stuffing tube) is used in certain applications. For example, when the U.S. Pat. No. '971 fitting or a stuffing tube is installed in a reactor bulkhead, the cross-sectional area of the channel or tube provides an unshielded path for gamma radiation. Special shielding techniques must be employed to compensate for these radiation paths. Also, when cables are to be passed across a pressure boundary, the right angle bend (in the U.S. Pat. No. '971 channels with side ports) is too extreme and fails to meet the design minimum bend radius for most cables.